This invention relates to synthetic fiberforming polyamides, and shaped articles therefrom, which have excellent affinity for basic or cationic dyestuffs.
It is an object of this invention to provide a new and useful polyamide. These polyamides are useful as shaped articles, particularly fibers which can be made into a textile fabric such as carpet. Another object is to provide a shaped article which has increased affinity to cationic dyes.
Ozone fading of cationic dyed polyamide yarn in carpet has become a serious problem to the industry. Another object is to provide a cationic dyed polyamide which has increased resistance to ozone fading, improved wash fastness and increased dyed lightfastness.
The salts of this invention are soluble in water, in contrast to the water-insoluble salts which are described as preferred in U.S. Pat. No. 3,665,054. The polysulfonic acids described in that patent have a lower degree of sulfonation, less than 50 percent, compared to the polysulfonic acid described here which is at least 90 percent sulfonated.
The salts of polystyrene sulfonic acid in which the styrene is sulfonated to a high degree have been reported to be insoluble in nylon. This insolubility is described in U.S. Pat. No. 3,553,286, which states that a vinyl polymer having pendant sulfonic acid groups in which the whole of the sulfonic acid group is present in the form of an alkali metal (Li, Na, or K) or calcium salt has bad compatibility with polyamide. We have confirmed that the sodium salt and the potassium salt do indeed have poor compatibility with nylon 6. This is shown below by Examples 1, 2, 3 and 4.
Also, in certain competitive dyeing situations, the cationic dyeable polymer yarn containing highly sulfonated polystyrene will pick up an undesired anionic dye. This undesirable pick-up is called cross staining.